The invention relates to an automated peritoneal dialysis system and process that provides a large supply of proportioned dialysis fluid which is used in a peritoneal dialysis system and process wherein the dialysis fluid is sterilized in-line with integrity checks in realtime during dialysis before delivery to a patient""s peritoneal cavity.
The National Institute of Health (NIH) reports that more than 289 people per million population in the United States require renal replacement therapy in the form of dialysis. The main barriers to treating dialysis patients have been expense and practicality. Moreover, the largest portions of the world""s population live in countries that do not support dialysis. Patients in those areas who need dialysis must pay for their own treatment, which leads to a sparing use of material that results in serious under dialysis and ineffective treatment. In the United States, the need for the patient to drive to a dialysis center for treatment, often over long distances, is a serious barrier to obtaining dialysis treatment for some needy patients. It is rather impossible to provide in-center dialysis to patients who cannot get to the clinic. Furthermore, in countries where there are few dialysis patients there is no highly trained and dedicated staff to care for the patients"" special needs. In short, the high cost of the current dialysis methods, massive supplies that must be delivered and stored for home dialysis, inadequate transportation, and a lack of trained professional healthcare workers capable of delivering dialysis treatment, are serious obstacles for dialysis patients.
There are two methods of clinical dialysis in widespread use today. They are called hemodialysis and peritoneal dialysis. They differ in the method by which the patient""s blood is exposed to the dialysate. Hemodialysis is the most widely used type of clinical dialysis. In this method, the patient""s blood is taken outside the body and passed through a dialysis cell, called a hemodialyzer. The hemodialyzer includes a membrane. The patient""s blood flows on a sterile side of the membrane while the dialysate flows along the opposite side. Dialysis of blood toxins and excess water occurs across the membrane. U.S. Pat. Nos. 5,683,584 and 6,074,559 disclose typical blood filters for use in hemodialysis to filter blood. This process requires the assistance of trained personnel and subjects the patient to life threatening dangers of mechanical malfunction, rapid shifts of fluid and metabolite, and surgery associated with attaching an artery directly to a vein to produce an adequate blood flow for dialysis treatment. Hemodialysis removes excess fluid from a patient by a process called ultrafiltration, which uses hydrostatic pressure to force water out of the blood, across the hemodialyzer, and into the dialysate for removal. It is also known to reuse blood filters after hemodialysis and to test the filter membrane when it is fully wetted with an aqueous solution using pressurized air to determine if there is a leak in the filter membrane, such as disclosed in U.S. Pat. No. 5,808,181.
Peritoneal dialysis was developed as a means of surmounting some of the difficulties associated with in-center hemodialysis. In addition, peritoneal dialysis is more suitable for in home use. In peritoneal dialysis, a specially prepared, sterilized dialysis fluid (dialysate) is instilled into the peritoneal cavity through an in-dwelling dialysis catheter. The toxins move down the gradient and into the dialysate, freeing the body of toxins. The dialysate is allowed to remain in the peritoneal space for a period, commonly called the dwell time, in order to maximize the quantity of toxins removed per unit volume of dialysate. Then, after absorbing body toxins in a long slow process, the dialysis fluid is removed and discarded. The longer the fluid remains in the cavity the less effective it becomes at removing waste due to the shift in the gradient towards equilibrium. The process is then repeated until the level of toxic metabolites in the blood is reduced to a desired level. This method is commonly referred to as the xe2x80x9cintermittentxe2x80x9d or xe2x80x9cbatchxe2x80x9d method due to the fact that multiple one or two liter bags of fresh, sterilized dialysis solution must be constantly exchanged to provide the supply of fresh, sterilized dialysate with an acceptable osmotic gradient. Peritoneal dialysis uses an osmotic gradient that is created by adding an osmol, usually glucose, to the dialysate to remove the patient""s excess fluid.
Commercially available, pre-sterilized peritoneal dialysate is expensive. Most patients have a peritoneal dialysis prescription of ten to fifteen liters per session, five to six times a week. However, this volume of fluid is frequently inadequate for the patient""s need but is all the patient can afford. The home peritoneal patient must have a large storage space in which to put the dialysis solution he will need until the next monthly shipment. On average, they must have the capacity to store about seventy-five to ninety gallons of dialysate to last the month. In addition, the patients must keep on hand a supply of other dialysis solutions with different glucose levels to meet changing body conditions.
Infection is one of the greatest dangers of peritoneal dialysis, either at home or in the hospital. Each time a sterile seal is broken, there is the danger of introducing bacteria into the system. Thus, each time a patient inserts a tube in a bag of fluid, or connects the tubing to his own in-dwelling catheter, or attaches the drainage bag, or does anything else which opens the system, there is the potential for contaminating the system and threatening the life of the patient. The more times the system must be opened, the greater the danger of contamination. The danger is actually compounded by fatigue, physical incapacity, and carelessness. The more often the patient must open the system, the less careful he becomes with each instance.
To overcome the above problems, various automated processes and systems for peritoneal dialysis have been proposed which seek to overcome the problems associated with the xe2x80x9cbatchxe2x80x9d method of peritoneal analysis. For example, U.S. Pat. Nos, 4,586,920, 4,718,890, 4,747,822, 5,004,459, and 5,643,201, issued to the present inventor, all relate to continuous or cyclic peritoneal dialysis systems and processes for overcoming the problems associated with effective home dialysis for needy patients. U.S. Pat. Nos. 4,586,920, 4,718,890, and 4,747,882 disclose single and double catheter peritoneal dialysis systems and methods which are automated in a continuous and cyclic manner. A reverse osmosis unit in combination with various filters produces sterilized water which is mixed with a dialysate in a conventional proportioning machine to produce a properly mixed dialysis solution. The dialysis solution is delivered through a high volume bacterial filter which sterilizes the dialysis solution. The sterilized dialysis solution is then stored in a head vessel for use in subsequent dialysis process. To test for sterilization, the dialysis solution may be cultured in the head vessel to see if a bacteria grows. U.S. Pat. No. 5,004,459 discloses an automated cyclic peritoneal dialysis system and process which automatically adjusts the osmoality of the dialysis fluid in response to the amount of excess fluid removed from the patent. Sterilized dialysis fluid is provided by mixing sterilized water and dialysate concentrate in a sterilized preparation unit. The dialysis preparation unit is disposed upstream of the dialysis machine which has been pre-sterilized with bleach or the like. U.S. Pat. No. 5,643,201 discloses an automated cyclictidal peritoneal dialysis system and process having a reverse osmosis unit for sterilizing water with a concentrate dialysate to produce a proportioned dialysis solution whereupon the dialysis solution is further sterilized by heating, and stored in a reservoir before use in the system and process. These prior systems and processes have mainly been directed to the provision of automatic control systems and processes having suitable controllers, valves, flow monitors, and pressure monitors to insure the dialysis process is safe for the patient. Emphasis has not been placed on providing an adequate, realtime source of sterilized dialysis fluid in an automated, peritoneal system and process which is closed. The provision of an adequate preparation and supply system for sterilized dialysis fluid in an automated peritoneal system and process for effective in home use has remained a problem. Since the intended use of a continuous or cyclic flow system is in a patient""s home, beyond the supervision of trained medial personnel, it is of primary importance that every effort be made to sterilize the system and fluids to protect the patient. Thus, given the present state of the art, there is a need for improvement.
Accordingly, an object of the present invention is to provide an automated peritoneal dialysis system and process wherein the dialysis fluid is reliably sterilized to provide a generally continuous supply of sterile dialysis fluid available on demand in a quick, simple, cost efficient manner.
Another object of the present invention is the provision of a generally continuous supply of sterilized dialysis solution for use in an automated peritoneal dialysis process wherein sterilization is achieved realtime in the flow line during the process and prior to patient entry in a reliable manner.
Another object of the present invention is to provide an automated cyclic peritoneal dialysis system and process using a flow-line sterilization filter and process which includes an integrity check for the filter to reduce the possibility of bacteria and other contaminants entering the patient""s peritoneal cavity.
Another object of the present invention is to provide an automated peritoneal dialysis system and process that adjusts the osmolality of the dialysate to achieve the prescribed amount of fluid removal best suited for the patient without having to switch between various bags of dialysate with different concentrations while sterilizing fluid as it is delivered to the patient, and to minimize the overall number of patient connections in the system.
Another object of the present invention is to provide a continuous peritoneal dialysis system and process having a high rate of dialysate exchange providing increased dialysis efficiency through the cost effective production of large volumes of dialysate.
The above objectives are accomplished according to the invention in a peritoneal dialysis system for performing continuous peritoneal dialysis of the type which includes delivering sterile dialysate to a patient, and removing spent dialysate, by providing an automated system and process having a large, generally constant supply of unsterilized dialysate ready on demand, wherein the dialysate is sterilized in realtime as the dialysate is delivered to the patent with back-up checks on the sterilization process. A fluid circuit is connected to the dialysate supply for delivering the dialysate to the patient and delivering spent dialysate from the patient to a drain. An inflow line segment of the fluid circuit delivers the dialysate from the supply to the patient during repeated fill cycles. Advantageously, at least one in-line sterilization filter assembly is disposed in the inflow line segment for real-time sterilization of the dialysate prior to delivery of the dialysate to the patient""s peritoneal cavity. An outflow line segment of the fluid circuit is provided for connection to the patient to drain spent dialysate from the peritoneal cavity during repeated drain cycles. A filter integrity test component is operatively associated with the sterilization filter assembly for conducting a realtime, in-line integrity test on the filter assembly to test for a filter failure condition which would allow contaminants into the dialysate prior to patient delivery. A test sensor in communication with the integrity testing component detects the failure condition. The sterilization filter assembly includes a main inlet port for receiving unsterilized dialysate during a dialysis mode, and receiving compressed air during a filter test phase, a sterilization filter medium through which the dialysate passes for producing sterilized dialysate, and an outlet port through which sterilized dialysate flows. The inlet and outlet ports are connected in the inflow line segment for delivery of the sterilized dialysate to the patient""s peritoneal cavity. Advantageously, the filter testing component may include a source of pressurized test air, and the fluid circuit includes a test line segment connected between a pressurized air source and the inlet port acting as an air admission port of the sterilization filter assembly. An air control valve maintains the inlet port normally closed to the admission of test air, and the air control valve has an open position for delivering the test air to the filter assembly during the integrity test so that a real time integrity test of the sterilization filter assembly can be made prior to the delivery of the dialysate to the peritoneal cavity.
The test sensor may sense a drop in pressure across the filter medium, and the failure condition comprises sensing a pressure drop rate, or decay, higher than a predetermined level indicating that the filter medium is not intact. Preferably, a delivery vessel is connected to the main outlet port of the sterilization filter assembly for accumulating the sterilized dialysate prior to delivery to the patient. There is a discard line segment included in the fluid circuit connected to the delivery vessel for discarding dialysate from the delivery vessel when the failure condition is sensed. In one aspect of the invention, the control valve is set in the open position for delivering the pressurized air to the inlet port of the filter assembly after the sterilized dialysate has been delivered to the delivery vessel and prior to delivery of the dialysate to the patient. In an advantageous embodiment of the invention, a sterilization unit having a primary sterilization filter assembly and a secondary sterilization filter assembly is disposed in the fluid circuit. The secondary filter assembly has a main inlet port connected to the delivery vessel for receiving sterilized dialysate, a sterilization filter medium for sterilizing the dialysate, and an outlet port for output delivery of the dialysate. The secondary filtration assembly may also comprise secondary test control valve for admitting test air to the secondary filter assembly. Again, the dialysate inlet port may also serve as the air admission port during the filter test mode. A secondary test sensor detects a failure condition of the secondary filter assembly upon the admission of test air for testing the integrity of the secondary filter assembly. Preferably, while dialysate is held in the delivery vessel, the test control valve associated with the primary filter assembly is set in an open position to admit pressurized test air, after the dialysate has passed through the primary filter assembly; and the secondary test control valve is set in an open position for admitting pressurized test air, before passage of dialysate through the secondary filter assembly. The post and pre tests of the primary and secondary filter assemblies are preferably done at the same time. The discard line segment discards dialysate in the delivery vessel when one or more of the filter assemblies fails the integrity test. In a advantageous aspect of the invention, a pair of sterilization units may be connected in parallel in the inflow line segment wherein each one of the sterilization units in the pair includes a primary and a secondary sterilization filter assembly, and a delivery vessel. A flow control means, such as a suitable valve arrangement, passes the dialysate through a selected one of the sterilization units while isolating the other of the sterilization units from the inflow line segment. In this manner, the two units may be used in a cyclic manner, that is, one of the sterilization units may be used during a current fill cycle, while the other unit is being used to prepare and sterilize dialysate for use in the next fill cycle. In addition one unit may be used alone while the other is down for replacement or other maintenance.
A system controller controls the amount of inflow and outflow during the fill and drain cycle. Preferably, the system includes a proportioning sensor responsive to the inflow and outflow volumes for determining a volume of body waste fluid removed from the patient""s peritoneal cavity during the fill and drain cycles. The system controller controls a proportioning component to adjust the osmolity of the dialysate in response to the volume of fluid, and controls the fill and drain cycles until a desired amount of waste fluid is removed from the patient.
According to the method of the invention, an automated peritoneal dialysis process includes an in-line, realtime dialysis fluid sterilization process to produce a sterilized dialysate. The sterilization process includes preparing an unsterilized dialysate effective for dialysis, passing the dialysate through at least one in-line sterilization filter assembly connected in an inflow line to the patient in realtime prior to delivery to the patient, and testing the sterilization filter assembly in realtime for a filter failure condition prior to delivering the dialysate to the peritoneal cavity of the patient. Preferably the dialysate is accumulated and held after passing the dialysate through the sterilization filter assembly, the integrity of the sterilization filter assembly is tested after passing the dialysate through the sterilization filter assembly, and the dialysate is discarded if the integrity test is failed. The process may also include providing a sterilization unit having a primary sterilization filter assembly and a second sterilization filter assembly, passing the dialysate through the primary sterilization filter assembly, accumulating the dialysate, testing the integrity of the primary and secondary sterilization filter assemblies, and passing the dialysate through the secondary sterilization filter assembly to the patient, if the tests are passed. The testing step may include testing the integrity of the primary filter assembly after passing the dialysate through the primary filter assembly, and testing the integrity of the secondary filter assembly before passing the dialysate through the secondary filter assembly. The dialysate is discarded after being accumulated if one or more of the filter assemblies fails the integrity test. In the automatic peritoneal dialysis process, dialysate is continuously delivered to the patient""s peritoneal cavity, and spent dialysate is removed from the patient. The automated process comprises the steps of: (a) providing a supply of unsterilized dialysate; (b) passing the unsterilized dialysate from the supply through an in-line sterilization filter assembly to produce sterilized dialysate in realtime prior to delivery to the patient""s peritoneal cavity; (c) accumulating the sterilized dialysate in a delivery vessel prior to delivery to the patient; (d) subjecting the in-line filter assembly to a filter integrity test to test for a filter failure that would allow contaminants into the dialysate prior to patient delivery; (e) delivering the sterile dialysate from the delivery vessel to the patient""s peritoneal cavity after the filter integrity test is passed; and (f) repeating steps (a) through (e) until a volume of fluid has been exchanged that both achieves the desired clearance and removes a desired fluid weight from the patient. Advantageously, this can be achieved by measuring the total volume of fluid removed several times during the dialysis session by completely draining the peritoneal cavity. This can be done by automatically measuring the difference in the fill and drain amounts. The automated system then calculates the rte of removal and increases or decreases the glucose concentration accordingly.
Advantageously, the dialysis fluid is accumulated and mixed in a mixing vessel where the correct proportions of acid, bicarbonate, and glucose are measured. While the batch of dialysis fluid is being prepared in the mixing vessel, an optional pre-process integrity test may be performed on the downstream sterilization filter assembly. After a successful integrity test, the newly prepared batch of dialysis fluid is sterilized by pumping it through the sterilization filter assembly and accumulated in a delivery vessel, after which a post-process integrity test is immediately performed. In the delivery vessel, the dialysis fluid is checked for proper concentrations of acid, bicarbonate, and glucose and heated to the correct delivery temperature. Following a successful post-process integrity test on the sterilization filter assembly, the dialysis fluid is pumped from the delivery vessel through a second sterilization filter assembly, which has passed an integrity test, and then into the patient""s peritoneal cavity. In another aspect, the invention includes an integrity test process that includes purging the upstream side of each sterilization filter assembly with sterile air, isolating the upstream side of the filter assemblies, allowing the pressure to stabilize, and monitoring the pressure decay for a given period of time whereby the rate of decay indicates the integrity of the filter assemblies. The patient is isolated from the integrity test by a 3-way valve upstream of the peritoneal port.